Hydroformylation reactions, commercially known as the oxo process, were discovered by O. Roelin in Germany and patented in 1943 (U.S. Pat. No. 2,327,066). The oxo process utilizes a cobalt catalyst, HCo (CO).sub.4, in the presence of syn gas having a 1:1 hydrogen to carbon monoxide ratio at a pressure of about 200 atmospheres, and at a temperature between about 120.degree. C. and 140.degree. C.
This hydroformylation results in the addition of hydrogen and carbon monoxide to the olefin to form an aldehyde. The aldehyde may then be reduced to form an alcohol.
Diolefins may be converted to dialcohols by this method. The dialcohols can be useful, for example, as monomers for condensation polymerization with diesters to form polyesters.
An improvement to the oxo process has been disclosed in U.S. Pat. No. 3,239,569. This improvement involved modification of the oxo catalyst with a phosphine ligand to form a cobalt complex. This improvement results in a significant yield of alcohol products directly from the hydroformylation without the need for a separate reduction step.
The oxo process has also been improved with respect to selectivity to straight chained alcohol or aldehyde products as suggested in U.S. Pat. No. 4,539,306. Patent '306 suggests that linear aldehydes or alcohols from olefins may be preferentially produced using a mixed transition metal hydroformylation catalyst wherein the catalyst comprises a mixture of transition metal compounds wherein the first component is an anionic transition metal catalyst having a charge of at least -2. The formula of the anionic compound is generally defined as M.sup.+n [H.sub.y A.sub.x L.sub.z ].sup.-n wherein A represents Fe, Ru, Os, W, Cr, Co, Rh, Ir, or Mo, M is a cationic species, n is an integer greater than or equal to 2, x is an integer greater than or equal to 1, y is an integer greater than or equal to 0 and z is an integer generally corresponding to the number of available coordination bonding sites of A. The component L is a Group VIII compound, preferably a halide or carbonyl of the Group VIII compound.
The mixed transition metal hydroformylation catalyst of U.S. Pat. No. 4,539,306 is not suggested to be selective to alcohols over aldehydes, but alcohols are preferentially produced by increasing the reaction temperature or the residence time. Increasing the residence time and/or the temperature is an unacceptable method to increase selectivity to linear alcohols because increasing side reactions compete with reduction of aldehydes to alcohols and limit the ultimate yield of linear alcohols.
1,9-Nonanediol can be produced by a method suggested in Japanese patent publication No. 2-243639 by hydroformylation of 2,7-octadien-1-ol using a rhodium catalyst system, and subsequent hydrogenation of the hydroformylation product. Considerably operating and capital costs are incurred by the additional hydrogenation step of the process of this patent publication.
Therefore there remains a need for a process to produce dialohols from starting materials such as alpha-alcohol-diolefins such as 2,7-octadien-1-ol wherein a increased residence time or temperature is not needed and wherein a one-step process can be utilized, and it is an object of the present invention to provide such a process.